Tunnel Design Methods covers analytical, numerical, and empirical methods for the design of tunnels in soil and in rock. The material is intended for design engineers looking for detailed methods, for graduate students who are interested in tunnelling, and for researchers working on various aspects of ground-support interaction under static and seismic loading. The book is divided into seven chapters, covering fundamental concepts on ground and support behavior and on ground-excavation-support interaction and provides detailed information on analytical and numerical methods used for the design of tunnels, with applications, and on the latest developments on empirical methods. The principles and formulations included are used, throughout the book, to provide insight into the response of tunnels under both simple and complex loading conditions, thus providing the reader with fundamental understanding of tunnel behavior. Both authors have experience in tunnelling and have worked extensively in practice, designing tunnels both in the United States and abroad, and in research.
The presence of organics in soils is generally associated with high compressibility, significant secondary compression, often unsatisfactory strength characteristics, and low unit weight. As a result of the above, many state DOTs (Departments of Transportation) in the United States have strict limits on the maximum value of the organic content (2-7%) that can be present in soils to be used as sub grades and backfills. The loss on ignition test is the most widely used technique for measuring organic content. However, especially for low organic content soils, this method can significantly overestimate the true organic content. As a result, certain soils may be incorrectly classified and erroneously considered unviable for certain applications; in other cases unnecessary costly treatments may be requested, even if not required. These are the issues motivating the research presented in this report, which addressed the classification of organic soils and the quantification of organic matter in soils. The research reviewed existing classification systems for organic soils, the effects of organic matter on the geotechnical properties of soils, and the methods for determination of organic content. In addition to the review of the existing literature, this research also included experimental work conducted on natural soils with varying organic content, as well as on laboratory prepared ("artificial") organic soils.
This field study investigates the degree of uniformity and quality that is obtained with soil modification with LKD (Lime Kiln Dust) using current construction techniques, and explores changes in construction methods that may result in a better product.
Lime is used to treat weak subgrade soils during construction of highways. A small amount of lime (4 to 7%) is used to rapidly dehydrate and modify fine grained soils. The modification process improves workability and compactability of the soils. Although the lime modification process is primarily aimed at construction expediency, additional effects such as long-term improvement of stiffness and/or strength by pozzolanic and carbonation cementation reactions are expected. Lime treatment has been employed in Indiana over several decades, but the long-term performance of lime-treated soils has not been well quantified and no field tests have been done on roads in service. A comprehensive field investigation was carried out to determine the properties of subgrade soils treated with lime in pavements that had been in service for at least five years. Six sites were selected for the field tests. At each site, SPT, DCPT, and FWD tests were performed to evaluate the in-situ stiffness and/or strength properties of the lime-treated subgrade. Laboratory tests from soil samples taken from the SPT spoon were done to obtain index properties of the lime-treated subgrade and the lime content that remains in the soil. The long-term performance of the lime-treated subgrade at each site has been evaluated by comparing the soil indices and stiffness and/or strength properties of the lime-treated subgrade soil with those of the natural soil. In addition, the lime content of the subgrade and the natural soil were measured to establish the remaining lime in the treated subgrade and detect any leaching in the underlying soil. The research has shown the following: (1) the lime remains in the soil even after 11 years of service of the road after construction; (2) the addition of lime decreases the plasticity of the soil and increases its CBR; and (3) the construction quality observed from the field tests is highly variable. 17.
Field and laboratory tests were conducted to investigate the degree of uniformity and quality that is obtained with chemical treatment of the subgrade with LKD using current construction techniques. An INDOT road project under construction was selected for the research. A 140-m long subgrade section was chemically treated with LKD with a target thickness of 16 inches, which is the current standard practice, while another 140-m long section was treated with a target thickness of 14 inches. DCP tests were done at each section to obtain the stiffness (or strength) of the chemically-treated and natural (untreated) subgrade soil layers. LWD tests were performed at the same locations where the DCP tests were done to estimate the stiffness of the treated subgrade layer. Nuclear gauge and sand cone tests were carried out to obtain the water content and dry density of the chemically treated subgrade. XRD and TGA tests were performed on soil samples collected in the field to identify and quantify the minerals contained in the soil. XRD and TGA laboratory tests show an adequate presence of lime in the subgrade, with somewhat better uniformity for the test site with 14 inches target thickness for the subgrade. Field tests, namely density, DCP and LWD, show consistently better and more uniform results for the 14 inches target thickness site than for the 16 inches target site. As a result of the research, it is recommended: (1) to increase for design the CBR of the subgrade treated with LKD by 25% over that of the natural soil; (2) to implement recommendation for a target thickness of the treated subgrade of 14 inches; (3) to introduce special, one type project where QC/QA is done by the contractor for design and construction, where full advantage of the subgrade improvement may be taken into consideration to minimize pavement thickness.
Tunnel Design Methods covers analytical, numerical, and empirical methods for the design of tunnels in soil and in rock. The material is intended for design engineers looking for detailed methods, for graduate students who are interested in tunnelling, and for researchers working on various aspects of ground-support interaction under static and seismic loading. The book is divided into seven chapters, covering fundamental concepts on ground and support behavior and on ground-excavation-support interaction and provides detailed information on analytical and numerical methods used for the design of tunnels, with applications, and on the latest developments on empirical methods. The principles and formulations included are used, throughout the book, to provide insight into the response of tunnels under both simple and complex loading conditions, thus providing the reader with fundamental understanding of tunnel behavior. Both authors have experience in tunnelling and have worked extensively in practice, designing tunnels both in the United States and abroad, and in research.
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